In the hydrometallurgical processing of vanadium slags and the recovery of vanadium pentoxide from the slag, the main phase of the slags -the spinellide -is the phase of the greatest interest from a commercial standpoint.Experience shows that the amount of spinellide which is present varies widely from one heat to the next -from 43 to 78%. This index affects not only the composition of the pig iron being made, but also the specifications of the chosen oxidant, the composition of the additions, the temperature of the pig, and other characteristics.To establish the relationship between the chemical composition of the converter slag and the concentration of spinellide, we statistically analyzed the results from a chemical analysis of a large number of slags. We analyzed about 30 railcars of converter slag that arrived at the shop over a period of 2-2.5 months. Chemical composition was determined by sampling the slag in accordance with the method adopted at the plant: crushing, followed by separation of metallic iron in the form of inclusions, scrap, and dispersed iron. To perform a petrographic analysis, five small samples of slag up to 80 mm in size were taken from each railcar load during the crushing operation. The results of the analysis were then averaged.The slags were divided into three groups based on the concentration of spinellide: nominally, 50%, 60%, and 70%; the actual concentrations were 51.3, 59.99, and 69.7%. The ranges of spinellide concentration in the different groups were 43.4-56.1, 57.2--62.0, and 65.1-78.8%, respectively. The chemical composition of the slags in each group was averaged over 10, 12, and 8 tests (Table 1).It can be seen from the table that metallic inclusions have the greatest effect on the concentration of spinellide. The mechanism of this effect is still unclear, but it can be stated that converter slag which contains no more than 19% metallic inclusions will have a spinellide content in the range 65-75%. A relationship was found to exist between spinellide content and the content of vanadium oxides, but it was not as explicit as had been expected. No relationship was found between spinellide content and the other components of the slag.The presence of spinellide in the slag is not by itself sufficient to be able to fully extract the vanadium in the slag during hydrochemical treatment. An equally important factor is the size of the spinellide grains that are formed. According to process specifications, the optimum grain size is within the range 10-15 Bm. Under production conditions, up to 60-70% of the total mass of spinellides consists of grains of 2.5-5.0 Bin. We assumed that spinellide grains were formed not only during the formation of the slag in the converter, but also during its cooling in air after tapping. To confirm this, we conducted an experiment to establish the effect of cooling time on the granulometric composition of the spinellides in converter slag; vanadium slag from recent commercial heats was used in the experiment. After being discharged from the furnace, ...
The oxidant usually used in the blowing of vanadium-bearing conversion pig irons in converters is a special agglomerate which ensures that the process of the removal of vanadium from the pig proceeds to completion. However, for several reasons, the composition and structure of the converter slag formed in this process does not always meet the requirements of the customers for this product.In particular, the slags formed at the Chusovoi Metallurgical Plant have a relatively high content of metal (in the form of inclusions, scrap, and dispersed iron), which increases the physical losses of the slag during separation and complicates the slag's chemical treatment during roasting and leaching. In addition, there are restrictions on the allowable concentrations of Cat, dispersed iron, and other components.In light of this situation, the plant has resorted to the use of briquets of a special composition to convert vanadium-bearing conversion pig iron. The briquets ensure that the main conditions required for the removal of vanadium from the pig will be created during the steelmaking operation. The briquets were prepared by pressing the raw material with a force of up to 200 kgf/cm 2. The strength of the finished briquets is sufficient to allow them to be transported, stored, and charged into the converter. They have a density of 2.3-2.6 tons/m 3 and a moisture content of 3.4-4.8%. Table 1 shows their chemical composition compared to sinter.The main difference between the composition of the briquets and the composition of the sinter is that the briquets contain alkalis (up to 2% Na20 ) and carbon (up to 5% crushed coke). We should also point out the relatively low content of iron oxides and the high content of Fe203 among the oxides in the briquets. The total content of oxides (Cr203 + V205 + Tit2) is more than twice as great as the content of oxides in the sinter.The process of removing vanadium from pig iron with the use of briquets having the composition shown in Table 1 was studied under production conditions at the Chusovoi plant by gradually replacing sinter with briquets until just briquets were being used in the conversion of vanadium-beating conversion pig iron (Table 2).Silicon, titanium, manganese, and chromium are oxidized in the same way as in the conventional process, regardless of the type of oxidant that is used. However, we should note that the relative concentrations of manganese and chromium present during the blow were somewhat higher -0.04--0.06% -when a high percentage of briquets was used. This trend is clearer when viewed from the standpoint of vanadium content -the degree of vanadium removal from the pig iron decreased from 92.1 to 79.1%. The oxidation loss of carbon also decreased: from 18-20 to 6-7%. Thus, the decarbonization reaction was slowed as expected, but so was the rate at which vanadium was removed from the pig iron.This raises the question of whether the result just described was related to the process of oxidation of the vanadium or to the V205 capacity of the converter slag. It is a...
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